1. Field of the Invention
The present invention relates to a lubricating device for an internal combustion engine. In particular, the present invention relates to an advantageous oil passage structure provided in a crank case of an internal combustion engine.
2. Description of Related Art
The provision of an oil passage in an engine has been made by piping a separate part such as a pipe in the engine (disclosed, for example, in Japanese Utility Model Publication No. Sho 62-42089); providing a groove in one of parting planes of a case and a cover and covering the groove with the other of the cage and cover, to form an oil passage; or forming a circumferential groove in a bearing surface of a bearing.
The above method of piping a separate part is disadvantageous in that the number of parts is increased. Furthermore, since the space for piping must be ensured, it is difficult to obtain a compact engine. The method of making use of the parting plane is disadvantageous in that it may be difficult to form a shorter oil passage because the position of the oil passage is limited to the parting plane. The method of forming a specialized oil passage by machining is disadvantageous in that such machining requires a special machining apparatus and the number of steps is increased. Furthermore, since a location at which the oil passage is to be formed must be ensured, it is difficult to obtain a compact engine.
An object of the present invention is to provide a lubricating device for an internal combustion engine, which is capable of solving above-identified problems of the related art.
To achieve the above object, according to the present invention, there is provided a lubricating device for an internal combustion engine in which a crank case is divided into first and second divided crank case parts, wherein oil is supplied from an oil pump provided in the first divided crank case part to portions to be lubricated, which portions are provided in the second divided crank case part, characterized in that the diameter of a fastening bolt hole, through which a bolt passes for fastening the first and second divided crank case parts to each other, is larger than the diameter of the bolt; and part of the bolt hole is communicated to another oil passage, to constitute part of an oil supply passage communicated to the second crank case part side.
According to the present invention, since an oil passage is formed by making use of part of a bolt hole through which a bolt passes for connecting two divided crank case parts (first and second divided crank case parts) of a crank case to each other, oil having been fed from an oil pump in the first divided crank case is supplied, via the oil passage in the bolt hole, to another oil passage for supplying the oil to portions to be lubricated of the second divided crank case part. As a result, special machining and special machining equipment are not required to form the oil passage; the number of parts is reduced; and since the location to be machined is not required to be set at a portion different from the bolt hole, the engine can be made compact. Furthermore, since part of the bolt hole used as the oil passage extends in the direction perpendicular to the parting planes of the divided crank case parts, another oil passage in communication with an oil pump in the first divided crank case can be in communication with an oil supply passage in communication with the second divided crank case part by way of the shortest oil passage composed of part of the bolt hole.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.